Lifter oil manifold assemblies (LOMAs) are hydraulic circuits generally known in the art and used in conjunction with Displacement on Demand (DoD) engines. The hydraulic circuit routes fluid pressure to solenoid control valves. When commanded by a powertrain control computer, the solenoids direct fluid to valve lifters equipped with a switching mechanism. The solenoids themselves are used as electromechanical devices or hydraulic switches to control fluid supplied to a control circuit when a particular solenoid is energized. The control circuit activates or deactivates a given valve lifter switch by controlling a control pressure applied to the switch; if the control pressure is high, for example, the valve lifter switch is turned on to operate the valve lifter.
When the automobile engine is turned off, air is often introduced into the hydraulic circuit as fluid from the control circuit drains back into the oil pan. This air must be bled out of the control circuit before activating any of the solenoids in the circuit to ensure proper, prompt response by the control circuit. If there is air trapped within the control system, it could create an unacceptable delay between the time the solenoid is energized and the time the control pressure changes in response. To avoid this, the air must be bled out within a specified time period to ensure that the control circuit will be ready for operation within a reasonable amount of time after the engine is turned on.
There is a desire for a hydraulic circuit that can bleed air out of the control circuit quickly and efficiently to optimize circuit performance.